It is important to control the moisture content of pulp insulated electrical conductors because if the pulp insulation is too wet it will deform during later handling and operation of the conductor and if it is too dry the insulation will flake. Also the electrical insulation resistance of the pulp varies in relation to the moisture content. The moisture content is dependent upon the heat of the oven which dries the pulp on the conductor and it may be altered subsequently by heating the conductors which have been made into cable form and wound onto a take-up reel.
In a conventional procedure the moisture content of the pulp is tested after the insulated conductor is wound on the take-up reel subsequent to leaving the drying oven. This is done by severing a sample length of the wound conductor, weighing the sample, heating the sample and weighing it again. In such a procedure a wide range of values must be tolerated if the moisture content varies throughout the length of the wound conductor. Also the delay occasioned by the procedure and the atmospheric moisture content may affect the test results.
To avoid the above-mentioned drawbacks it would be advantageous to test the moisture content of pulp insulation on electrical conductors during the process of applying the insulation but any electrical test which has been formulated has proven unsatisfactory because of the presence of stray charges on the pulp which makes the readings of the test unpredictable. By stray charges we mean all voltages due to static charges, induced electromotive forces and thermoelectric voltages.
It is an object of the present invention to provide an improved method of testing the moisture content of pulp insulation on an electrical conductor during the application of the insulation onto the conductor.
It is a further object of the invention to provide an improved apparatus for testing the moisture content of pulp insulation on an electrical conductor during the application of the insulation onto the conductor.